Spotlight on… lactic acid

With lactic acid commonly used in skincare, we speak to some experts to find out more about the science behind it, and how best it can be used

How does lactic acid work?

Lactic acid is commonly used in topical skincare. These days, it is usually synthetically made in a lab, but it was traditionally created as a natural by-product of plant and dairy fermentation. Like glycolic acid, lactic acid is an alpha-hydroxy acid (AHA). AHAs are a type of exfoliating acids that are water-soluble and able to penetrate the upper layers of the skin. They have become increasingly popular over the last decade in skincare products aimed at minimising signs of skin ageing. They work by eliminating dead skin cells to help improve the skin’s overall appearance and texture.

Lactic acid has a number of benefits for the skin, including its gentle exfoliation properties. “Lactic acid causes the breakdown of the desmosomes, which are skin-binding enzymes, to induce surface cells to be released, stimulating the exfoliation process,” says Rebecca Jones, Noon Aesthetics educator and ambassador. “The deeper layer of skin is stimulated to increase the synthesis of collagen and glycosaminoglycans – the skin’s water carriers.”

Lactic acid has a larger molecule size than some of the other AHAs, such as glycolic acid, so it is gentler and can't penetrate as far into the skin. This means that it has most of its exfoliating effects on the skin's surface.

“Lactic acid is a natural component of the skin's acid mantle, which is a thin, protective film on the surface of the skin that helps maintain its pH balance, and acts as a barrier against harmful bacteria and environmental stressors,” says Andrea O'Donnell, DIBI Milano national educator.

“Lactic acid adjusts the pH of the skin, making it slightly more acidic. The acidic environment helps to weaken the bonds that hold the dead skin cells together, denaturing proteins and promoting the shedding of dead skin cells on the surface of the skin. This process improves skin texture, brightens the complexion, unclogs pores and allows for better absorption of products. An interesting fact about lactic acid is that it is produced by the body as a by-product of glucose metabolism, and it is also naturally present in sweat.”

What can lactic acid help with?

Lactic acid is a great treatment for pigmentation and uneven skin tone as well as dry, dehydrated and dull skin. It can also reduce the appearance of fine lines and help stimulate ceramide formation to help strengthen the skin's barrier function.

“Its exfoliating properties promote cell turnover, improving skin tone and reducing the appearance of discoloration, and stimulate collagen production, improving the appearance of fine lines and wrinkles,” notes O'Donnell. “Lactic acid also has humectant properties, which means it attracts and retains moisture in the skin.”

In addition, there is scientific evidence that shows that lactic acid can boost the skin's vitality. “Research shows that treatment with 12% lactic acid resulted in increased epidermal and dermal firmness and thickness, and clinical improvement in skin smoothness and the appearance of fine lines and wrinkles,” explains Cigdem Kemal Yilmaz, a chemical engineer, skincare formulator and the founder of Skin Masterclass.

'Lactic acid is a natural component of the skin's acid mantle, which is a thin, protective film on the surface of the skin that helps maintain its pH balance'

“No dermal changes were observed after treatment with 5% lactic acid; however, similar clinical and epidermal changes were noted. The clinical evidence indicates that the topical application of lactic acid is effective for depigmentation and improving the roughness and mild wrinkling of the skin caused by environmental photodamage.”

How should it be used?

Because lactic is a gentle exfoliant, it can be found in a multitude of home-use skincare products, including cleansers, toners and serums – so there are plenty of opportunities for your clients to include lactic acid in their routines.

“Lactic acid can be used in various skincare products, but serums are the most concentrated formulas that deliver a potent dose of lactic acid to the skin, offering a targeted treatment for particular skin concerns,” says O'Donnell. “It's important to note that regardless of the form, it is advisable to start with lower concentrations of lactic acid and gradually increase usage as tolerated.”

Lactic acid can also boost the effects of other in-salon treatments. “It works well to complement an aesthetic procedure, such as needling and injectables,” says Jones. “While you would not perform the treatments together, their benefits work in harmony to achieve results.”

While it’s important not to overprocess the skin by using too many exfoliants and active ingredients at the same time, lactic acid can be safely layered with most skincare ingredients, such as salicyclic or hyaluronic acid. “I love layering lactic acid with vitamin C, amino acids, panthenol and green tea extract,” says Yilmaz.

Are there any contraindications?

If a client has very sensitive skin, then lactic acid can be irritating and shouldn't be used on those who suffer from eczema, psoriasis and rosacea. “Easily irritated skin may experience adverse reactions to lactic acid, therefore it is important to perform a patch test before using it,” says O'Donnell. “You should avoid using lactic acid on sunburned or injured skin as it may cause further irritation.”

Other issues could occur if the lactic acid used in skincare products is derived from dairy and clients have a dairy allergy or intolerance – so it’s important to always check the provenance of these products and to carry out a pre-treatment consultation with clients in order to ascertain any potential contraindications. It is also not recommended to layer lactic acid with retinoids because this can irritate the skin.